Spark plug



A. TEBALDI SPARK PLUG Filed April 27, 1,932

Nov. 21,;1933.

y Patented Nov. 21, 1933 UNITED STATES PATENT oFFlcE Application April 27, 1932, Serial No. 607,822, and in Germany August 11, 1931 12 Claims.

"l0 pating means, are substantially invariable and therefore they cannot equally comply with thermal conditions prevailing in low speed and with those prevailing in full speed operation of the engine.

The object of the present invention is to provide a spark plug able to meet such requirement. In accordance with the present invention a spark plug for internal combustion engines is provided which comprises an auxiliary heat sensitive s and conducting member which is adapted to establish or suppress, according to the temperature it is subjected to due to conditions ofV operation of the engine, a supplemental thermal connection between the plug heat dissipating means and the parts of the same which are heated because of the engine operation in such a manner as the plug automatically maintains a substantially conl stant temperature throughout the full working range ofthe engine.

Embodiments of the present invention are hereinatter described by way of example with reference tofaccompanyna drawing in which:

, Figure 1 is a longitudinal central section of a construction of a plug according with this inven- '35 tion;

. Figure 3 is an end view of a separate member?.

f of the plug as hereinafter described;

through a further embodiment of said plug.

In the embodiment` of Figure 1, theplug comprises a screwthreaded hollow body 1 adapted to be screwed, as usual, into the wall ot an engine 4'5 cylinder. A hollow central electrode 8 is'mounted in body 1 by meansof a nut .2 screwed in said body 1 and intermediate insulating parts 4 and 5; I a connecting and heatdissipating head 11 is fastened on the top of electrode 8 by means of a 5o cap 7 screwed on electrode 8 and an insulating member 6 is located intermediate nut 2 and head 11. Electrode 8 provides a sparking point 9 which is adjacent ,-to and cooperates with a sparking point 10 extending inwardly from the wall of hollowbodyl.

Figure 4 is a longitudinal central section (Cl. 12S-169) Within the hollow electrode 8 a rod 13 is fastened by its end 14 screwed in the electrode point 9 and an ample gap is left intermediate facing outer and inner surfaces of rod 13 and electrode 8. The end of said rod 13 opposed to its connect- 60 ing end 14 is in front of cap 7 and a gap 15 is provided intermediate the top face 13 of said rod and opposite bottom face 7 of cap 7.

Assuming the respective lengths and sizes of parts 8 and 13 and the materials of which each 65 of them is made are suitably chosen, when the temperature of the plug is below a predetermined value the top face 13 of rod 13 remains spaced from opposite face 7 of cap 7 and then no heat transference may arise from rod 13 to cap '7 and 70 heat dissipating head 11, the heat transference from heated portion 9 of electrode to said heat dissipating head taking place solely through body of electrode 8; on the contrary, when electrode 9, 8 is more strongly heated rod 13 expands and 75 its top face 13 engages opposite face 7 of cap 7, heat being thus conveyed to dissipating head 11 through the electrode body 8 and rod 13.

The described plug therefore provides two different conditions forvheat dissipation and plug cooling in respect of diilerent running conditions of the engine, and thus the temperature and operation of the plug are maintained satisfactorily uniform throughout the full running range of the engine.

Figures 2 and 3 show a similar condition in which rod 13 is prevented from exerting a longitudinal thrust on plug parts 7 and 11 which could seriously aiect theV mounting and interconnection of the parts of the spark plug.

In this construction cap 7 provides a tapering downwardly projecting part 16 in its internal face opposite the top face of rod 13, and said rod 13 has at its free end a tapering recess 17 and transverse slots 18 providing resilient teeth 19; the other parts of the plug are the same as described in connection with Figure 1.

On rod 13 extending under heat action, teeth 19 of rod engage tapering portion 16 of the cap 7 and thus they magnify the heat transmission from electrode 8 to heat dissipating head 11, without an axial thrust being operative on projection 16, cap 7 and head 11, because said teeth are caused to resiliently bend outwardly at the time they are engaging tapering projection 16.

In both constructions of Figure 1 and of Figure 2 the respective or diierential elongations of electrode 8 and rod 13 may depend upon the fact that they take up different temperatures because electrode 8 is subject to a large heat dissipation towards external air while rod 13 is entirely protected against heat radiation; therefore parts 8 and 13 may be made of the same metal.

However said parts 8 and 13 may be made of materials having diierent thermal extensions in order to magnify their diierential elongations.

Figure 4 shows a further embodiment in which a bimetallic member is used to provide the rod having one end secured on electrode 8, said bimetallic member consisting of two strips 13a, 13b made of metals having diierent coefficients of thermal extension or elongation and located adjacent to each other with their contacting faces soldered on each other at 13". Said member 13a, 13b provides an inclined face 13'. located opposite a face 20 of a metal member 21'fastened within cap '7 by having a flange 2l' .engaged between the end of hollow electrode 8 and the bottom face 7' of cap 7. On the plug being moderately heated faces 13 and 20 of unit 13a, 13b and member 21 respectively.

What I claim as my invention and desire to secure by United States Letters Patent isz- 1. A spark plug for internal combustion engines comprising a plug body, an electrode fastened in and insulated from said body, heat dissipating means connected with said electrode, a heat sensitive member connected with said electrode and extending toward said heat dissipating s means and cooperating contact means on said heat dissipating means and member for resilient engagement of the same with each other, said contact means being spaced when said electrode and member are under a given temperature and being carried into contact by said heat sensitive member due to its modification under effect of heat when the temperature of said electrode and member is above a given value. l

2. A spark plug for internal combustion engines comprising a-plug body, an electrode fastened in and insulated from said body, heat dissipating means connected with said electrode, a heat sensitive member connected with said electrode and extending toward said heat dissipating means and cooperating contact means on said heat dissipating means and member for resilient engagement of the same with each other, said contact means comprising a split member and a tapering member engaging into said split member, and said contact means being spaced when said electrode and member are under a given temperature and being carried into engagement by said heat sensitive member due to its modication under effect of heat when the temperature of said electrode and member is above a given value. p A

3. A spark plug for internal combustion engines comprising a plug body, a hollow electrode fastened in and insulated from said body, heat dissipating means connected with said electrode, a heat sensitive member loosely located within said electrode' and connected with its sparking point and extending towards said heat dissipating means, and cooperating contact means on said heat dissipating means and member for resillent engagement of the same with each other, said contact means comprising a split member and a tapering member engaging into said split member, and said contact means being spaced `when said electrode and member are under a given temperature and being carried into engagement by said heat sensitive member due to its modication under effect of heat when the temperature of said electrode and member is above a given value.

4. A spark plug for internal combustion engines, comprising a plug body, an electrode fastened in and insulatedfrom said body, heat dissipating means, and a heat sensitive member connected with said electrode and extending toward said heat dissipating means, said heat dissipating means and heat sensitive member having cooperating contact faces, said contact faces being spaced from each other when said heat sensitive member is heated a't a given temperature during the operation of the plug and coming into contact with each other due to the modiiication of said heat sensitive memberwhen said heat sensitive member is heated to a temperature above said first temperature.

5. A spark plug for internalvcombustion` engines, comprising a plug body, an electrode fastened in and insulated from said body, -heat dissipating means connected with said electrode, and a heat sensitive member connected with said electrode and extending toward said heat dissipating means, said heat dissipating means and heat sensitive member having cooperating contact faces, said contact faces being spaced from each other when said heat sensitive member is heated at a given temperature during the operation of the plug and coming into contact with each other due to the modification of said heat sensitive member when said heat sensitive member is heated to a temperature above said nrst temperature.

6. A spark plug for internal combustion engines, comprising a plug body, an electrode fastened in and insulated from said body, heatdissipating means, a bimetallic unit connected with said electrode and extending towards said heat dissipating means, said heat dissipating means and unit having cooperating contact faces. said contact faces being spaced from each other when said unit is heated at a given temperature during the operation of the plug and coming into contact with each other on said unit having its coniiguration altered under the effect of heat when said unit is heated to a temperature above said temperature. Y v

7. A spark plug for internal combustion engines, comprising a plug body, an electrode fas` tened in and insulated from said body, heat dissipating means, a bimetailic unit connected with said electrode and extending towards said heat dissipating means, said heat dissipating means and unit having cooperating sloping contact faces, said sloping contact vfaces beingv spaced from each other when said unit is heated-at a given ltemperature during the operation of the plug and coming into contact with .each other on said unit having its configuration altered under the effect of heat when said unit is heated to a temperature above said irst temperature;

8. A spark plug for internal combustion engines, comprising a plug body, a hollow electrode fastened in and insulated from said body, heat dissipating means, and a heat sensitive member loosely located within said electrode and connected with its sparking point and extending toy :,esaaes' ward said heat dissipating means, said heat dissipating means and heat sensitive member having cooperating contact faces, said contact faces being spaced from each other when said heat sensitive member is heated to a given temperature during the operation of the plug and coming into contact with each other due to the modification ci said heat sensitive member when said heat sensitive member is heated to another temperature above said nrst temperature.I

9. A spark plug for internal combustion engines, comprising a plug body, a hollow electrode fastened in and insulated from said body, heat dissipating means connected with said electrode, and a heat sensitive member loosely located within said electrode and connected with its sparking\point and extending toward said heat dissipating means, said heat dissipating means and heat sensitive member having cooperating contact faces, said contact faces being spaced from each other when said heat sensitive member is heated at a given temperature during the operation of the plug and coming into contact with each other due to the modiiication o! said heat sensitive member when said heat sensitive member is heated to another temperature abovey said first temperature.

10. A spark plug for internal combustion engines, comprising a plug body, a hollow electrode fastened in and insulated from said body, heat dissipating means, a heat sensitive member loosely located within said electrode andv connected with its sparking point and extending toward said heat dissipating means, and cooperating contact` means on said heat dissipating means and heat sensitive member for resilient engagement of the same with each other, said contact means being spaced from each other when said heat sensitive member is heated at Plug a given temperature during the operation of the and coming into contact with each other due to the modification of said heat sensitive member when said heat sensitive member is lheated to another temperature above said first temperature.

11. A spark plug ,for internal combustion engines, comprising a plug body, a hollow electrode fastened in and insulated from said body, heat dissipating means, and a bimetallic unit loosely located within said electrode and connected with its sparking point and extending towards said heat dissipating means, said unit and heat dissipating means providing cooperating contact faces, said contact faces being spaced from each other when said heat sensitive member is heated at a given temperature during the operation ot the plug and coming into contact with each other due to the modification of said heat sensitive member when said heat sensitive member is heated to another temperature above said first temperature.

12. A spark plug for internal combustion engines, comprising a plug body, a hollow electrode fastened in and insulated from said body. heat dissipating means, and a bimetallic unit loosely located within said electrode and connected with its sparking point and extending towards said heat dissipating means, said unit and heat dissipating means providingl sloping faces for contact with each other, said sloping contact faces being spaced from each other when said heat sensitive member is heated at a given temperature during the operation of the plug and coming into contact with. eachother due to Ythe modication of said heat sensitive member when said heat sensitive member is heated to another temperature above said first temperature.

ALESSANDRO TEBALDI. 

